|Wireless remote data
Technologies and sample systems that gather sensor data across distances, usually via radio links. This includes general telemetry and SCADA (supervisory control and data acquisition), especially for gathering data about wildlife, natural resources, and distributed energy systems.
Thursday, May 27, 2004
Embedded Linux marches on: "One of the cheapest Linux computers you can buy brand new (not at a garage sale) is the Linksys WRT54G, an 802.11g wireless access point and router that includes a four-port 10/100 Ethernet switch and can be bought for as little as $69.99 according to Froogle. That's a heck of a deal for a little box that performs all those functions, but a look inside is even more amazing. There you'll find a 200 MHz Intel processor and either 16 or 32 megs of DRAM and four or eight megs of flash RAM -- more computing power than I needed 10 years ago to run a local Internet Service Provider with several hundred customers. But since the operating system is Linux and since Linksys has respected the Linux GPL by publishing all the source code for anyone to download for free, the WRT54G is a lot more than just a wireless router. It is a disruptive technology. ..
it isn't what the WRT54G does that matters, but what it CAN do when reprogrammed with a different version of Linux with different capabilities. .. Linksys, now owned by Cisco, not only doesn't mind your hacking the box, they are including some of those hacks in their revised firmware...
Probably the most popular third-party firmware you can get for the WRT54G comes from Sveasoft .. [whose] head techie is James Ewing.. If you have a WRT54G, here's what you can use it for after less than an hour's work. You get all the original Linksys functions plus SSH, Wonder Shaper, L7 regexp iptables filtering, frottle, parprouted, the latest Busybox utilities, several custom modifications to DHCP and dnsmasq, a PPTP server, static DHCP address mapping, OSPF routing, external logging, as well as support for client, ad hoc, AP, and WDS wireless modes. .. The parts of this package I like best are Wonder Shaper and Frottle. Wonder Shaper is a traffic-shaping utility that does a very intelligent job of prioritizing packets to dramatically improve the usability of almost any broadband connection [by prioritizing voice and optionally a particular user's traffic. Frottle also prioritizes traffic.] .. Neither Wonder Shaper nor Frottle are the most elegant solutions, but they work well and they work together on the Sveasoft firmware. ..
The result is a box [that] automatically attaches itself to an OSPF mesh network that is self-configuring. In practical terms, this mesh network, which allows distant clients to reach edge nodes by hopping through other clients en route, is limited to a maximum of three hops as the WiFi radios switch madly back and forth between sending and repeating modes. If you need to go further, switch to higher-gain antennas or gang two WRT54Gs together. Either way, according to Ewing, his tests in Sweden indicate that if 16 percent of the nodes are edge nodes (wireless routers with DSL or cable modem Internet connections), they can provide comparable broadband service to the other 84 percent who aren't otherwise connected to the Net." Cringley then speculates on how to take on phone companies with this. 11:22:56 PM
Codan experience in Guinea-Bissau Elections: "The National Elections Commission of Guinea-Bissau used new Information and Communication Technology tools to coordinate the legislative elections held March 28 and enable poll workers to verify names and identity card numbers on the voter rolls. .. The project was designed by Sila Technologies (SITEC), a private company, and funded by a grant from the European Economic Community.
About a week before the elections, SITEC had up and running high frequency (HF) radio units in all nine regional capitals of Guinea-Bissau and verified that they could communicate with each other via voice, fax, or data transmission over up to 200 kilometers. Fax transmission was reported to be flawless, and voice communication was functional. According to SITEC engineer Amidu Sila, some level of noise is to be expected in using this technology and frequency range for voice, though this never impeded communication. ..
The company chose radios made by Codan Ltd., model NGT SR, for the project, along with a system that automatically selects and switches between available frequencies to get the best transmission. The HF units reportedly cost around $7,000 each, and the additional link management system goes for about $1,200. Before beginning installation, SITEC had to be assigned twenty available HF-band frequencies, which they chose together with the regulatory agency. Half of the frequencies were for use during the day, and the other half for the different atmospheric conditions of nighttime. Sila thinks that the radio could work over distances as far as 1500 kilometers." 12:34:57 PM
: "Relief workers are often encumbered by poor Internet connectivity, fragile or expensive equipment, or security concerns associated with collecting detailed geographic data in areas recovering from conflict. As connectivity expands and the tools get cheaper and more diverse, the specific needs of relief workers in the field are increasingly being met. Companies such as Global Relief Technologies
and Groove Networks appear to point the way." 12:24:53 PM